Inter partes review (IPR) has become a popular procedure for challenging the validity of patent claims. The Patent Trial and Appeal Board (PTAB), however, may only cancel a patent claim as invalid only under 35 U.S.C. § 102 (anticipation) or 35 U.S.C. § 103 (obviousness). Furthermore, only patents and printed publications may be used to establish anticipation or obviousness.1 A petitioner, for example, may not argue that a patent is invalid under § 101 or § 112. In order to address the IPR, the PTAB, however, may be required to focus on issues other than § 102 and § 103. While the PTAB may not cancel a patent claim under the written description and definiteness requirements of § 112, an analysis related to these statutory requirements may be determinative—or at least highly relevant—in an IPR proceeding. For example, the written description and definiteness requirements of 35 U.S.C. § 112 may be relevant to determining the meaning of a claim at issue in an IPR. As another example, the written description requirement may be relevant to determining the priority of a claim at issue.

Written Description and Definiteness Requirements are Relevant to Claim Interpretation

The PTAB institutes an IPR in response to an IPR petition only if “the information presented in the petition . . . shows that there is a reasonable likelihood that the petitioner would prevail with respect to at least 1 of the claims challenged in the petition.”2 In determining whether to institute an IPR, the PTAB construes the claim, and the claim is given its broadest reasonable interpretation in light of the specification.3 A claim term is given its ordinary and customary meaning, as would be understood by one of ordinary skill in the art in the context of the entire disclosure.4 Thus, the PTAB must consider the specification to construe the claims.

The disclosure is particularly relevant when a challenged claim includes a means-plus-function or step-plus-function limitation. To construe one of these limitations, the PTAB “must identify the specific portions of the specification that describe the structure, material, or acts corresponding to the claimed function.”5 The specification must thus adequately describe the “structure, material, or acts” corresponding to a means-plus-function or step-plus-function limitation for the PTAB to institute an IPR. While the PTAB lacks authority to invalidate a patent claim based on a finding that the specification does not adequately support a means-plus-function or step-plus function limitation, the PTAB may refuse to institute an IPR if it cannot construe the claim at issue, such as when the specification fails to disclose a structure that corresponds to the claimed function.6

In ETS-Lindgren Inc. v. Microwave Vision, S.A., the PTAB refused to institute IPR proceedings because the claim failed to meet the written description requirement and could not be interpreted. The claim at issue recited “means for pivoting one or more of the network of probes and the support.”7 The PTAB determined that this claim element includes “pivoting both the network of probes and the support.”8 The PTAB noted that one embodiment described pivoting the network of probes and another embodiment described pivoting the support, but that the specification did not support a combination of the two structures.9 The PTAB therefore determined that the claim could not be interpreted and refused to institute the IPR proceeding.10

Written Description Requirement is Relevant to Determining Priority

As another example, the PTAB may perform a written description analysis to determine the priority of a claim at issue. To be entitled to the priority of a parent application, the claimed invention must have been disclosed in the parent application in a manner that satisfies the written description requirement of § 112(a).11 That is, the specification of the parent application must describe the claimed invention sufficiently to allow a person of ordinary skill in the art to understand that the inventor was in possession of the claimed subject matter at the time of the parent application.12

In certain circumstances, determining whether a patent claim is valid under § 102 or § 103, requires a determination of the priority date of the claim in question and thus also requires the PTAB to determine whether a parent application meets the written description requirement of § 112(a). For example, if the PTAB determines that the parent application does not meet the written description requirement, the claim in question receives a later priority date. This increases the amount of prior art references that may be used to invalidate the claim under § 102 and § 103.

The PTAB performed this very analysis in Daiichi Sankyo Co., Ltd. v. Alethia Biotherapeutics, Inc.13 The parties agreed that a reference, Hiruma, taught each and every element of the instituted claims. The parties disputed, however, the priority date of the instituted claims, requiring the PTAB to perform a § 112 analysis to determine the claims’ priority date.

The patent that included the instituted claims was filed on October 16, 2009. The patent owner argued that the claims were entitled to priority from a parent application filed on February 13, 2007.14 The Hiruma reference became available as prior art on April 16, 2009.15 The Hiruma reference, therefore, would not be prior art to the instituted claims if the instituted claims had a priority date of February 13, 2007. The PTAB performed the § 112 analysis and determined that the parent application failed to “sufficiently describe common structural information to show possession [of the limitations recited] in the challenged claims.”16 Thus, the instituted claims did not receive the earlier priority date and were invalidated by the Hiruma reference.


Although the PTAB may not have the authority to invalidate patent claims based on § 112 in an IPR proceeding, the PTAB may perform a § 112 analysis or an equivalent analysis. Thus, arguments relating to § 112 may, in certain circumstances, affect the outcome of an IPR proceeding. As such, both petitioners and respondents should consider § 112 when handling IPR proceedings before the PTAB.